Sedimentary facies and depositional model of shallow water delta dominated by fluvial for Chang 8 oil-bearing group of Yanchang Formation in southwestern Ordos Basin,China

A systematic analysis of southwestern Ordos Basin's sedimentary characteristics,internal architectural element association styles and depositional model was illustrated through core statistics,well logging data and outcrop observations in Chang 8 oil-bearing group.This analysis indicates that shallow water delta sediments dominated by a fluvial system is the primary sedimentary system of the Chang 8 oil-bearing group of the Yanchang Formation in southwestern Ordos Basin.Four microfacies with fine grain sizes are identified: distributary channels,sheet sandstone,mouth bar and interdistributary fines.According to the sandbody's spatial distribution and internal architecture,two types of sandbody architectural element associations are identified: amalgamated distributary channels and thin-layer lobate sandstone.In this sedimentary system,net-like distributary channels at the delta with a narrow ribbon shape compose the skeleton of the sandbody that extends further into the delta front and shades into contiguous lobate distribution sheet sandstone in the distal delta front.The mouth bar is largely absent in this system.By analyzing the palaeogeomorphology,the palaeostructure background,sedimentary characteristics,sedimentary facies types and spatial distribution of sedimentary facies during the Chang 8 period,a distinctive depositional model of the Chang 8 shallow water fluvial-dominated delta was established,which primarily consists of straight multi-phase amalgamated distributary channels in the delta plain,net-like distributary channels frequently diverting and converging in the proximal delta front,sheet sandstones with dispersing contiguous lobate shapes in the distal delta front,and prodelta or shallow lake mudstones.

High resolution facies architecture and digital outcrop modeling of the Sandakan formation sandstone reservoir, Borneo:Implications for reservoir characterization and flow simulation

Advances in photogrammetry have eased the acquisition of high-resolution digital information from outcrops, enabling faster, non-destructive data capturing and improved reservoir modeling. Geocellular models for flow dynamics with in the virtual outcrop in siliciclastic deposits at different sets of sandstone facies architecture remain, however, a challenge. Digital maps of bedding, lithological contrast, spatial-temporal variations of bedding and permeability characteristics make it more easy to understand flow tortuosity in a particular architecture. An ability to precisely model these properties can improve reservoir characterization and flow modeling at different scales. Here we demonstrate the construction of realistic 2 D sandstone facies based models for a pragmatic simulation of flow dynamics using a combination of digital point clouds dataset acquired from LiDAR and field investigation of the Sandakan Formation, Sabah, Borneo.Additionally, we present methods for enhancing the accuracy of outcrop digital datasets for producing high resolution flow simulation. A well-exposed outcrop from the Sandakan Formation, Sabah, northwest Borneo having a lateral extent of 750 m was chosen in order to implement our research approach. Sandstone facies and its connectivity are well constrained by outcrop observations, data from air-permeability measurements, bilinear interpolation of permeability, grid construction and water vector analysis for flow dynamics.These proportions were then enumerated in terms of static digital outcrop model(DOM) and facies model based on sandstone facies bedding characteristics. Flow simulation of water vector analysis through each of the four sandstone facies types show persistent spatial correlation of permeability that align with either cross-bedded orientation or straight with more dispersion high quality sandstone(porosity 21.25%-41.2%and permeability 1265.20-5986.25 mD) and moderate quality sandstone(porosity 10.44%-28.75% and permeability 21.44-1023.33 mD). Whereas, in more heterolithic sandstone(wavy-to flaser-bedded and bioturbated sandstone), lateral variations in permeability show spatially non-correlated patterns over centimeters to tens of meters with mostly of low quality sandstone(porosity 3.4%-12.31% and permeability < 1 mD to 3.21 mD). These variations reflect the lateral juxtaposition in flow dynamics. It has also been resulted that the vertical connectivity and heterogeneities in terms of flow are mostly pragmatic due to the interconnected sandstone rather than the quality of sandstone.

Research on 3D Distribution of Meandering River Sand Body Using Sedimentary Facies Method and 3D Geological Modeling

Sedimentary facies study is an important method in describing the property and distribution of reservoir. 3D geological modeling is a powerful tool in 3D characterization of geological bodies. By combining the sedimentary facies study with 3D geological modeling to generate 3D sedimentary facies model, the 3D geometry and distribution feature of sand bodies can be more accurately characterized, particularly in 3D view. In Liuchu oilfield of Jizhong depression, the Ed2IV formation was recognized as meandering river deposition facies and five sedimentary facies were identified, which include point bar sand, levee, channel margin, abandoned channel and floodplain. All the 24 sand body facies in Ed2IV were mapped and the 3D sedimentary facies model established based on 2D facies maps. The result shows that the 3D sedimentary facies model is well matched for the research result of sedimentary facies. Being an extension of traditional sedimentary study, the 3D sedimentary facies model can be used to describe the 3D geometry and distribution orders of a single sand body more reliably and more accurately.

Classification and Facies Sequence Model of Subaqueous Debris Flows

Objective Debris flows are cohesive sediment gravity flows which occur in both subaerial and subaqueous settings. Compared to subaerial debris flows which have been well studied as a geological hazard, subaqueous debris flows showing complicated sediment composition and sedimentary processes were poorly understood. The main objective of this work is to establish a classification scheme and facies sequence models of subaqueous debris flows for well understanding their sedimentary processes and depositional characteristics.

Phase equilibrium modelling of the amphibolite facies metamorphism in the Yelapa-Chimo Metamorphic Complex, Mexico

The Yelapa-Chimo Metamorphic Complex forms part of the Jalisco Block in western Mexico and exposes a wide range of Early Cretaceous metamorphic rocks;such as paragneiss,orthogneiss,amphibolites,and migmatites.However,the pressure-temperature(P-T)conditions of metamorphism and partial melting remain poorly studied in the region.To elucidate metamorphic P-T conditions,phase equilibrium modelling was applied to two sillimanite-garnet paragneisses,one amphibole-orthogneiss,and one amphibolite.Sillimanite-garnet paragneisses exhibit a lepidoblastic texture with a biotite+sillimanite+kyanite+garnet+quartz+plagioclase+K-feldspar mineral assemblage.Amphibole-orthogneiss and amphibolite display a nematoblastic texture with an amphibole+(1)plagioclase+quartz+(1)titanite assemblage and an amphibole+(2)plagioclase+(2)titanite+ilmenite retrograde mineral assemblage.Pseudosections calculated for the two sillimanite-garnet paragneiss samples show P-T peak conditions at~6-7.5 kbar and~725-740℃.The results for amphibole-orthogneiss and the amphibolite yield P-T peak conditions at~8.5-10 kbar and~690-710℃.The mode models imply that metasedimentary and metaigneous units can produce up to~20 vol%and~10 vol%of melt,respectively.Modelling within a closed system during isobaric heating suggests that melt compositions of metasedimentary and metaigneous units are likely to have direct implications for the petrogenesis of the Puerto Vallarta Batholith.Our new data indicate that the Yelapa-Chimo Metamorphic Complex evolved through a metamorphic gradient between~23-33℃km^-1and the metamorphic rocks formed at depths between~22 km and~30 km with a burial rate of~2.0 km Ma^-1.Finally,the P-T data for both metasedimentary and metaigneous rocks provide new constraints on an accretionary framework,which is responsible for generating metamorphism and partial melting in the YelapaChimo Metamorphic Complex during the Early Cretaceous.

Sedimentary Microfacies and Porosity Modeling of Deep-Water Sandy Debris Flows by Combining Sedimentary Patterns with Seismic Data： An Example from Unit I of Gas Field A, South China Sea

Sandy debris flow deposits are present in Unit I during Miocene of Gas Field A in the Baiyun Depression of the South China Sea. The paucity of well data and the great variability of the sedimentary microfacies make it difficult to identify and predict the distribution patterns of the main gas reservoir, and have seriously hindered further exploration and development of the gas field. Therefore, making full use of the available seismic data is extremely important for predicting the spatial distribution of sedimentary microfacies when constructing three-dimensional reservoir models. A suitable reservoir modeling strategy or workflow controlled by sedimentary microfacies and seismic data has been developed. Five types of seismic attributes were selected to correlate with the sand percentage, and the root mean square （RMS） amplitude performed the best. The relation between the RMS amplitude and the sand percentage was used to construct a reservoir sand distribution map. Three types of main sedimentary microfacies were identified： debris channels, fan lobes, and natural levees. Using constraints from the sedimentary microfacies boundaries, a sedimentary microfacies model was constructed using the sequential indicator and assigned value simulation methods. Finally, reservoir models of physical properties for sandy debris flow deposits controlled by sedimentary microfacies and seismic inversion data were established. Property cutoff values were adopted because the sedimentary microfacies and the reservoir properties from well-logging interpretation are intrinsically different. Selection of appropriate reservoir property cutoffs is a key step in reservoir modeling when using simulation methods based on sedimentary microfacies control. When the abnormal data are truncated and the reservoir properties probability distribution fits a normal distribution, microfacies-controlled reservoir property models are more reliable than those obtained from the sequence Gauss simulation method. The cutoffs for effective porosity of the debris channel, fan lobe, and natural levee facies were 0.2, 0.09, and 0.12, respectively; the corresponding average effective porosities were 0.24, 0.13, and 0.15. The proposed modeling method makes full use of seismic attributes and seismic inversion data, and also makes the property data of single-well depositional microfacies more conformable to a normal distribution with geological significance. Thus, the method allows use of more reliable input data when we construct a model of a sandy debris flow.

Iterative static modeling of channelized reservoirs using history-matched facies probability data and rejection of training image

Most inverse reservoir modeling techniques require many forward simulations, and the posterior models cannot preserve geological features of prior models. This study proposes an iterative static modeling approach that utilizes dynamic data for rejecting an unsuitable training image(TI) among a set of TI candidates and for synthesizing history-matched pseudo-soft data. The proposed method is applied to two cases of channelized reservoirs, which have uncertainty in channel geometry such as direction, amplitude, and width. Distance-based clustering is applied to the initial models in total to select the qualified models efficiently. The mean of the qualified models is employed as a history-matched facies probability map in the next iteration of static models. Also, the most plausible TI is determined among TI candidates by rejecting other TIs during the iteration. The posterior models of the proposed method outperform updated models of ensemble Kalman filter(EnKF) and ensemble smoother(ES) because they describe the true facies connectivity with bimodal distribution and predict oil and water production with a reasonable range of uncertainty. In terms of simulation time, it requires 30 times of forward simulation in history matching, while the EnKF and ES need 9000 times and 200 times, respectively.

Sedimentary Facies Controls on the Upscaling of Petrophysical Properties from Core to Log Scales and Its Implications to Petroleum Exploration

The clastic sedimentary realm comprises a number of genetically distinct depositional systems, which are dominated by distinct depositional processes. A variogram and a Levy-stable probability distribution-based geostatistical method have been applied to analyze petrophysical properties from well logs and cores from a variety of depositional environments in sedimentary basins from Australia to quantify the heterogeneity and upscaling range of different depositional systems. Two reservoir sequences with contrasting sedimentary facies, depositional processes and a diagenetic history are investigated for their petrographic, petrophysical and log characters and their scaling behaviour. The microscopic derived petrophysical parameters, including visual porosity, grain size, sorting and amount of matrix, core plug measured porosity and permeability and log-derived V-shale, porosity and permeability, have been found to be well correlated (|R|=0.72 to 0.91) across all the scales for the reservoir sequence deposited under a single predominant depositional process and a gradational change of the energy regime (Bilyara-1). In contrast, for the reservoir sequence (East Swan-2), which was deposited in heterogeneous processes and underwent diagenetic alteration, the cross-correlation of the petrophysical properties derived from the three different scales is extremely poor (|R|=0.01-0.54). Log-derived porosity and permeability for a thinly bedded reservoir sequence with an individual bed thinner than one metre can therefore be affected by the intrinsic averaging effects of the logging tools.

Integration of Sequence Stratigraphic Analysis and 3D Geostatistical Modeling of Pliocene–Pleistocene Delta,F3 Block,Netherlands

This research is focused on the analysis of the sequence stratigraphic units of F3 Block,within a wave-dominated delta of Plio–Pleistocene age.Three wells of F3 block and a 3D seismic data,are utilized in this research.The conventional techniques of 3D seismic interpretation were utilized to mark the 11 surfaces on the seismic section.Integration of seismic sequence stratigraphic interpretation,using well logs,and subsequent 3D geostatistical modeling,using seismic data,aided to evaluate the shallow hydrocarbon traps.The resulting models were obtained using System Tract and Facies models,which were generated by using sequential stimulation method and their variograms made by spherical method,moreover,these models are validated via histograms.The CDF curve generated from upscaling of well logs using geometric method,shows a good relation with less percentage of errors(1 to 2 for Facies and 3 to 4 for System Tract models)between upscaled and raw data that complements the resulted models.These approaches help us to delineate the best possible reservoir,lateral extent of system tracts(LST and/or HST)in the respective surface,and distribution of sand and shale in the delta.The clinoform break points alteration observed on seismic sections,also validates the sequence stratigraphic interpretation.The GR log-based Facies model and sequence stratigraphy-based System Tract model of SU-04-2 showed the reservoir characteristics,presence of sand bodies and majorly LST,respectively,mainly adjacent to the main fault of the studied area.Moreover,on the seismic section,SU-04-2 exhibits the presence of gas pockets at the same location that also complements the generated Facies and System Tract models.The generated models can be utilized for any similar kind of study and for the further research in the F3 block reservoir characterization.

Development Model and Quantitative Prediction of Igneous Rock in S Oilfield, the Bohai Sea Area

The structure of S Oilfield of Bohai sea area in China is located in the low uplift slope zone of the Dongwa Laibei area in the Huanghekou depression. The target interval of the oilfield belongs to the Paleogene layered structural oil reservoir under the influence of igneous rocks. Due to the widespread development of igneous rocks, and the diversity of igneous rock types, the structure is complex, and the lateral changes are intense. The differences in volcanic eruption intensity and volcanic materials made the igneous rock masses overlap each other, with rapid changes in lithofacies, and complex seismic reflection structures. Therefore, it was difficult to carry out fine characterization of igneous rocks. Based on the lithofacies model, lithofacies combination types, and seismic response characteristics of volcanic mechanisms, this paper summarized three types of development models of volcanic mechanisms in the study area. At the same time, through technical means such as stratigraphic slicing, seismic attribute extraction, and attribute optimization analysis, the spatial distribution characteristics of various facies zones of igneous rocks at different stages were described in detail, achieving precise prediction of igneous rocks in Bozhong S Oilfield. During the development process of the oilfield, the technical research results guided the optimization of well locations and provided technical support for the efficient development of the oilfield.

鄂尔多斯盆地石盒子组-山西组致密储层形成主控因素与发育模式:以彬长地区为例

明确致密储层“甜点”的分布是致密储层油气勘探的重点。通过岩心观察、薄片鉴定、X射线衍射、包裹体均一温度测定、常规物性分析等手段,对鄂尔多斯盆地南部彬长地区上古生界致密砂岩沉积特征、储层特征、成岩作用进行了详细研究,明确了储层形成的主要控制因素并建立了优质储层的发育模式。结果表明:沉积相是储层形成的基础,辫状河三角洲平原分流河道心滩微相岩石粒度粗,孔隙结构为小孔-中细喉型,储层物性相对较好;曲流河三角洲前缘水下分流河道及河口坝微相岩石粒度细,孔喉结构为微孔-微喉型,储层物性相对较差。成岩作用对优质储层的发育与分布具有重要控制作用。间歇性火山凝灰质在酸性地层蚀变为高岭石,而在碱性地层蚀变为绿泥石套膜,抑制了石英次生加大和方解石胶结,保护了储集空间。石英次生加大主要为泥岩转化形成的SiO_(2)渗滤到砂岩中形成的,中晚期方解石充填长石、岩屑溶孔为方解石顶底板胶结的主要原因。晚期构造改造形成的微裂缝无方解石胶结,改善了储层物性,对气藏起调整作用。彬长地区在3 750 m和3 900 m埋深段附近为2个溶蚀孔发育带。最优储层为溶蚀孔发育带内火山凝灰质转化形成的富含绿泥石套膜的中-粗砂岩;次优储层主要分布在溶蚀孔发育带内单砂体厚度较大、有旋回且无泥岩隔档的砂体的中下部,主要为缺少绿泥石套膜的中-粗砂岩,方解石胶结与石英次生加大作用最低。研究成果进一步深化了鄂尔多斯盆地南部地区上古生界致密砂岩优质储层发育的成因,对该地区天然气勘探开发具有重要指导意义。

珠江口盆地白云凹陷东部古近系文昌组沉积演化特征

充分利用新三维地震资料,结合测井以及录井资料,对珠江口盆地白云凹陷古近系文昌组层序地层、沉积特征及沉积演化进行研究,重新建立文昌组三级层序格架内的沉积体系演化过程。结果表明:白云凹陷东部文昌组自下而上共划分为5套三级层序,分别对应于初始裂陷期(WCSQ1)、拆离裂陷早期(WCSQ2,WCSQ3)、拆离裂陷晚期(WCSQ4,WCSQ5)3个构造演化阶段;初始裂陷期为多个孤立的箕状半地堑,以发育缓坡轴向物源辫状河三角洲、陡坡近源扇三角洲和滨浅湖沉积为特征;拆离裂陷早期断裂活动强烈,湖盆迅速扩张,半深湖—深湖局限发育,沉积中心北移,北部番禺低隆起发育大型辫状河三角洲沉积;拆离裂陷晚期断裂活动减弱,湖盆逐渐萎缩,沉积中心稳定在白云凹陷中部,主要发育小型辫状河三角洲沉积,滨浅湖发育;大型辫状河三角洲及扇三角洲砂体是白云凹陷东部的有利储集体。

油气储层勘探建模技术新进展及未来展望

油气储层建模利用地质统计学等方法,综合测井、地质、地震等多学科信息,是油气田开发研究的利器,油藏地质模型可以将油藏各种地质特征在三维空间的变化及分布定量表征出来,是油气藏的类型、几何形态、规模、油藏内部结构、储层参数及流体分布的高度概括,储层地质模型是油藏地质模型的核心,可以对储层的沉积特征、非均质性、物性及流体等特征进行综合表征。但在勘探阶段,面对大尺度沉积体系和稀疏井网条件下的储层展布规律表征的建模难点为:①地质知识的量化表达问题,包括地质专家的经验认识如何数字化表征。②稀疏井网条件下无法直接用钻井资料对地质体的发育规模、展布方向和结构特征准确定量描述及构建地质模式,大尺度空间中复杂沉积体系无法用简单数学函数表征。③传统地质统计学等方法在勘探模型构建中如何实现地震、测井、地质、油藏等多维度数据的融合问题。因此,基于确定性建模和传统地质统计学等随机建模的储层建模理论和技术遇到极大挑战。笔者在系统剖析传统储层建模技术流程和方法的基础上,通过构建涵盖地质、测井、地震、分析化验等信息的多学科地学大数据知识库,开展多维数据凝聚层次聚类的沉积相模式库表征和基于生成式网络的智能建模,提出了多学科协同的油气储层勘探建模技术对策及技术体系,实现了构造、沉积及储层之间匹配关系的定量表征。该技术体系在东营凹陷北部陡坡带、洼陷带勘探部署中开展系统应用,构建融合古地貌、古物源、搬运通道、测井及地震属性等多信息的岩相、物性及油气运聚的地质模型,基于模型新范式指导部署井位,支撑了陆相断陷盆地复杂砂砾岩体、页岩油等勘探实践。笔者通过深度剖析东营凹陷北部陡坡带勘探建模实践难点及精度问题,进一步探讨了未来油气储层勘探建模技术发展趋势和应用前景。

龙门山中段北川通口剖面中二叠统栖霞组地层沉积特征

川西龙门山前带栖霞组是近期油气勘探的热点,龙门山中段栖霞组勘探程度低,明确其地层沉积特征,对于天然气勘探具有重要的指导意义。基于对龙门山中段北川通口剖面实测,结合薄片鉴定和主量、微量元素分析,对栖霞组层序地层及沉积特征进行了研究,明确了沉积环境。北川通口剖面梁山组—栖霞组识别出2个三级和1个四级层序界面,划分为1个三级层序和2个四级层序。梁山组—栖霞组发育滨岸—沼泽、开阔台地及台地边缘3种沉积相,开阔海、滩间海、台内滩和台缘滩4种亚相,台内生屑滩、台缘生屑滩和台缘砂屑、生屑滩3种微相。栖一段至栖二段下部整体处于开阔台地,栖二段中上部则处于台地边缘,建立了龙门山中段栖霞组镶边碳酸盐岩台地沉积模式。栖霞组沉积期整体处于温暖、湿润、富氧、古生物大量繁殖的海水—陆表海沉积环境,栖二段中上部高位体系域Sr/Ba比值整体最低,MgO/CaO比值最高,平均古水温高,V/(V+Ni)、V/Cr低值,古盐度m值明显较高,代表远离陆地的浅水、高能台地边缘沉积环境,厚大高能台缘砂屑、生屑滩发育,是规模优质滩相孔隙型白云岩储层发育有利部位。龙门山中段栖二段与北段、南段具有相似的沉积相带和储集条件,是栖霞组油气勘探的有利区带,有望成为实现规模增储的重要战略接替阵地。

游荡型辫状河沉积特征及沉积相模式

针对冀东油田高104 5区块馆陶组辫状河模式认识不清、砂体预测不准的问题,开展砂质辫状河河型分类研究。首先,根据区域地质背景、古气候、岩石粒度、层理构造、相序、溢岸、落淤层发育情况以及砂体形态等指标确定研究区为游荡型辫状河。随后,以Miall构型要素分析理论为指导,建立了辫流带、单一辫流带内河道和心滩边界识别标志,实现了研究区游荡型辫状河结构解剖,确定研究区单一辫流带宽度平均1 400.00 m,单一辫流带内心滩平均长度为414.47 m,宽度平均为158.86 m,河道宽度平均53.18 m。心滩长宽比集中在2.0~4.0,心滩宽度与辫状河道宽度比为2.2,为宽坝窄河道辫状河沉积模式。最后采用沉积数值模拟的方法,建立了研究区游荡型辫状河沉积相模式,可为油田开发提供指导。

柴北缘欧龙布鲁克地块中元古代晚期麻粒岩相变质作用——来自石榴夕线堇青石片麻岩的岩石学、相平衡模拟和U-Pb年代学的制约

在欧龙布鲁克地块乌兰北部地区察汗河岩群中识别出麻粒岩相石榴夕线堇青石片麻岩,其矿物组合为石榴子石、夕线石、堇青石、黑云母、斜长石、钛铁矿和少量钾长石等。岩相学观察显示,M1阶段矿物组合有斜长石±钾长石+石榴子石+夕线石+石英,M2阶段矿物组合有斜长石±钾长石+石榴子石+夕线石+石英+钛铁矿+黑云母,M3阶段矿物组合有堇青石+黑云母+钛铁矿+石英+石榴子石+斜长石±钾长石。相平衡模拟计算结果显示,该岩石的峰期温压条件为p=0.92~1.08 GPa,峰期温度t>790℃,峰期之后经历升温降压的p-T演化轨迹。锆石和独居石LA-ICP-MS U-Pb年代学研究获得的变质年龄分别为1133±14 Ma和1125±37 Ma,1133~1125 Ma应代表了该期麻粒岩相变质作用的时代。结合区域地质资料和已有的研究成果,我们认为乌兰北部察汗河岩群的石榴夕线堇青石片麻岩可能形成于大洋俯冲作用下的弧或弧后构造环境,乌兰北部的岩浆-变质杂岩带经历了从中元古代晚期-新元古代早期俯冲增生到碰撞造山的演化过程,是全球Rodinia超大陆汇聚过程的响应。

海相细粒沉积成因机制与有机质富集模式研究进展

综合分析了国内外细粒沉积的特征、成因及有机质富集模式研究进展。海相细粒沉积主要由黏土矿物、石英、碳酸盐矿物和有机质组成,受风力、异轻流、重力流和底流4大搬运营力作用,发育泥纹层和粉砂纹层2类纹层,单一型、顺序型和交互型3类纹层组(层系),块状层、递变层和交互层3类层(层组)。海相细粒沉积发育浊流沉积、底流沉积及远洋-半远洋沉积3种主要沉积相类型及其过渡类型。海相细粒沉积有机质存在高生产力和强保存2种富集模式,高生产力富集模式下黑色页岩主要通过“上升洋流”、“氧含量最低值区(OMZ)”和“近岸透光带缺氧(PZE)”模式形成高有机质富集,强保存富集模式下黑色页岩主要通过“受限盆地”、“改进的受限盆地”、“不规则底形”、“水洼扩张”、“海侵化变层”和“近岸海侵(TN)”模式形成高有机质富集。目前海相细粒沉积成因机制与相模式研究存在的主要问题包括名词术语不规范、不同矿物成分成因不明确,以及细粒浊流沉积、等深流沉积和半远洋沉积难以区分,需要今后进一步研究解决。

准噶尔盆地沙湾凹陷三叠系百口泉组沉积相展布特征及沉积模式

准噶尔盆地沙湾凹陷三叠系百口泉组主要发育扇三角洲沉积,准确识别扇三角洲各沉积相的展布特征对多类型油气藏的勘探开发具有重要意义。结合高精度三维开发地震和大量钻井、测井资料,采用沉积相研究、地震属性分析和古地貌恢复等方法,对沙湾凹陷百口泉组沉积相展布特征进行了研究。研究结果表明:①沙湾凹陷百口泉组可划分出3个四级层序和数个五级层序,且3个四级层序分别对应百口泉组的3个层段,五级层序受短期沉积旋回控制,分别对应不同的沉积微相。②均方根振幅属性对岩性变化更为敏感,能量高值区对应扇三角洲平原亚相,中值区对应扇三角洲前缘亚相,低能量区对应滨浅湖亚相。③百一段和百二段沉积时期,研究区湖盆面积小,主要发育扇三角洲平原和前缘亚相;百三段沉积时期湖盆面积增大,主要发育扇三角洲前缘和滨浅湖亚相,为典型的水进退积型扇三角洲。扇三角洲前缘亚相物性较好,被滨浅湖亚相的泥质岩所覆盖,形成良好的储盖组合。④研究区百口泉组扇体规模大、物源近,岩性以砂砾岩为主,为缓坡浅水扇三角洲沉积模式,扇三角洲前缘亚相为潜在的有利成藏区,是油气资源规模发现的重点勘探区。

松辽盆地徐家围子断陷沙河子组沉积相类型及演化模式

【目的】徐家围子断陷沙河子组致密砂砾岩储层具有非常大的天然气勘探潜力,有望成为大庆油田深层火山岩气藏勘探的重点接替领域。【方法】综合运用岩心、录井、测井及地震等资料,对徐家围子断陷沙河子组沉积相展布及沉积演化模式开展了研究。【结果与结论】徐家围子断陷沙河子组发育辫状河三角洲、扇三角洲、具供给水道的远岸浊积扇、近岸水下扇、扇三角洲前端滑塌浊积扇以及浅湖—半深湖、深湖相等沉积相。安达凹陷、徐东凹陷以及肇州凹陷东侧的缓坡带接受来自肇东—朝阳沟基底古隆起的碎屑物质而发育辫状河三角洲沉积,局部发育由远源供给水道形成的湖底浊积扇沉积体;安达凹陷、徐东凹陷、徐西凹陷以及肇州凹陷西侧等徐西陡坡带接受来自中央隆起带粗碎屑物而发育扇三角洲沉积体系,以近源短流为基本特征,局部发育近岸水下扇沉积,且由于湖盆边缘发育的扇三角洲沉积体不稳定,在扇三角洲沉积体前方形成滑塌浊积扇沉积。

渤海湾盆地莱州湾凹陷南斜坡中生界火山岩相模式和储层特征

精细岩相模式是油气藏研究的重要基础,为储层预测和评价提供合理的约束。目前火山岩还缺少微相尺度的相模式。参照的5相15亚相分类方案,在莱州湾凹陷南斜坡中生界火山地层中建立了相—亚相—微相划分方案,识别出3相4亚相10微相。具体为爆发相的热碎屑流亚相和热基浪亚相,细分为火山口-近火山口、近源和远源微相。喷溢相熔岩流亚相,细分为简单熔岩流和碎屑堆积微相。火山-沉积相崩塌再搬运堆积亚相,细分为再搬运块状堆积和基质堆积微相。钻井揭示研究区的亚相占比从高到低的顺序为爆发相热基浪亚相、喷溢相熔岩流亚相、爆发相热碎屑流亚相和火山-沉积相崩塌再搬运堆积亚相。火山地层具有复杂岩相叠置关系,亚相单元横向延伸范围有限、对比难度大。储层孔渗条件由好到差的顺序为热基浪亚相、热碎屑流亚相、熔岩流亚相和崩塌再搬运堆积亚相。热基浪亚相近源微相、热碎屑流亚相近源微相、熔岩流亚相简单熔岩流微相上部、崩塌再搬运亚相块状堆积微相的储层较好;其中,热基浪亚相近源微相储层条件为最优。本研究可为火山岩储层预测和评价提供地质依据。